1. Field of the Invention
This invention relates to air pressure operated time keeping devices.
2. Discussion of Related Art
U.S. Pat. No. 4,170,869, which is the inventor's own prior patent, discloses an air operated hour clock having an axially displaceable rotor mounted in a cylindrical housing with a shaft extending axially from the housing which mounts an indicator hand. In operation, the rotor, shaft and indicator are displaced axially of the housing and rotate through engagement of coacting teeth spaced circumferentially of the housing and rotor. Various problems have been encountered arising from the axial movement of the entire shaft and pointer. For instance, when the shaft moves axially, a portion thereof is exposed externally of the housing and can collect dust, dirt, etc., causing the shaft to stick in the displaced position. This, of course, detrimentally affects the functioning of the clock.